My CS2 would not calibrate. I used the mouse and got to the calibration screen but touching the cross hairs would not register. The first one would register after many attempts. I was in a real panic as the warranty ran out last month ( 16 days ago).
I called the Marklin customer service number here in Germany . The service rep told me this was a common issues and the technicians suggested vacuuming or using dust off on all of the openings. She said that the vast majority of returned units with faulty touch pads were repaired by cleaning dust out of the unit.
The vacuum cleaner did the trick. Several minutes of vacuuming did the trick. What a relief!!!
Hope this info helps others.

Keep that screen clean and if you have fat fingers like mine just use a stylus to interact with your CS2. Or better yet just use a mouse to control the CS2 - that is a huge improvement and it is very easy to do.